The present invention relates in general to light detectors and in particular to a new and useful device for detecting the occurrence and direction of laser radiation.
Such devices, usually termed "laser warning sensor", are known and may or may not include directional detection. For example in an article by B. T. Ballard published in the periodical "Laser Focus", April '81, a laser warning system is described which may be called an interferometric warning sensor with direction analysis. It is further known, from German Pat. No. 28 30 308, to determine the direction of incidence of laser radiation, by means of various angular arrangements, from the different signal levels of the detectors.
German Pat. No. 29 31 818 discloses a device of the above mentioned kind comprising a ring arrangement through which the signal passes in opposite directions and the direction of incidence is determined from the time difference between the two passages. This device is not suitable for processing optical signals and the technology is very problematic. Also, it requires individual photodetectors for every direction of incidence.
All these prior art devices and methods have several drawbacks. Either their field of sight is limited and a panoramic monitoring can be ensured but at very high costs, or the angular resolution is too small, particularly at unfavorable directions of incidence. Frequently, even the shape of the laser signal is distorted by a time integration in the detector, which which makes it very difficult to recognize the impending threat. In some of the prior art devices, high sensitivity to disturbances or angular errors casued by partial soiling of the optical apertures produce adverse effects, or the adaptability to different laser wavelengths is restricted.